Toyota Celica 2005, Repair Manual

Page: 348 / 2497

A20489
A21204
Fuel compensation
amount
1.35
1.0
0.65
+35 (%): Threshold at LEAN
− 35 (%): Threshold at RICH
− DIAGNOSTICS ENGINE (1ZZ − FE)
DI − 149
2005 CELICA (RM1131U)
MONITOR DESCRIPTION
Under closed − loop fuel control, fuel injection amount that deviates from the ECM’s estimated fuel amount
will cause a change in the long − term fuel trim compensation value. This long − term fuel trim is adjusted when
there are persistent deviations in the short − term fuel trim values. And the deviation from a simulated fuel
injection amount by the ECM affects a smoothed fuel trim learning value. The smoothed fuel trim learning
value is the combination of smoothed short
− term fuel trim (fuel feedback compensation value) and
smoothed long − term fuel trim (learning value of the air − fuel ratio). When the smoothed fuel trim learning val-
ue exceeds the DTC threshold, the ECM interprets this as a fault in the fuel system and sets a DTC.
Example:
If the smoothed fuel trim learning value is more than 1.35 or less than 0.65, the ECM interprets this as a
malfunction in the fuel system.
MONITOR STRATEGY
Related DTCs
P0171 Fuel system lean (Bank 1)
P0172 Fuel system rich (Bank 1)
Required sensors/components
Main sensors/components Front oxygen sensor
Related sensors/components
Engine coolant temperature sensor, Mass air flow
meter, Crankshaft position sensor
Frequency of operation Continuous
Duration 10 sec.
MIL operation 2 driving cycles
Sequence of operation None
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